1. Field of the Invention
The present invention relates to acetoxymethylacenaphthylene, hydroxymethylacenaphthylene, a polymer prepared from the acetoxymethylacenaphthylene or hydroxymethylacenaphthylene, and an antireflection film-forming composition comprising the polymer suitable for use in microfabrication using a lithography process which utilizes various radiations, particularly for manufacturing highly integrated circuit elements.
2. Description of Background Art
Production of polyacenaphthylene by polymerizing acenaphthylene and production of copolymers by copolymerizing acenaphthylene with styrene, maleic anhydride, or the like are well known in the art.
Such acenaphthylene polymers and copolymers (hereinafter collectively referred to as (co)polymers) are highly reactive due to their unique structure. Chemical reactions of such (co)polymers with various reactive reagents have been investigated and details of their properties such as luminous actions have been reported. Various materials possessing properties such as low hygroscopicity, low birefringence, and low dielectric constant, as well as utilization of such materials have been developed.
Providing acenaphthylene derivatives possessing various functional groups useful as raw materials for manufacturing acenaphthylene (co) polymers is very important from academic and industrial viewpoints in developing the acenaphthylene (co)polymers that are highly reactive and expected to have various characteristics. Various acenaphthylene derivatives having an aromatic ring substituted with a hydroxyl group, alkyl group, halomethyl group, halogen, or the like have already been synthesized.
However, no acenaphthylene derivatives having an aromatic ring substituted with an acetoxymethyl group or hydroxymethyl group have been reported heretofore.
The fabrication size in a lithography process for manufacturing integrated circuit elements is becoming smaller to achieve a higher degree of integration. In the lithography process, a resist composition solution is applied to a substrate, a mask pattern is transcribed on the resist by a stepper (reducing projection aligner), and the resist is developed using a suitable developer to obtain a desired pattern. However, the substrate having a high reflectance such as aluminum, aluminum-silicon alloy, aluminum-silicon-copper alloy, polysilicon, or tungsten silicide used in this process reflects radiation on the surface and produces halation on a resist pattern, making it impossible to precisely reproduce a fine resist pattern.
To overcome this problem, a method of providing an antireflection film that can absorb radiation reflected on the surface of the substrate under the resist film to be formed on the substrate has been proposed. Inorganic films such as a titanium film, titania film, titanium nitride film, chromium oxide film, carbon film, and α-silicon film formed by vacuum deposition, CVD, sputtering, or the like are known as such an antireflection film. These inorganic antireflection films, however, have drawbacks such as conductivity which precludes these films from being used for production of integrated circuits and requirement of a special apparatus for forming such as a vacuum deposition apparatus, CVD apparatus, and sputtering apparatus.
As a material overcoming these drawbacks of inorganic antireflection films, an organic antireflection film made from a polyamide acid (co)polymer or polysulfone (co)polymer and a dye has been proposed (see Japanese Patent Application Laid-open No. 59-93448, for example). This organic antireflection film has no conductivity. In addition, since the composition from which the film is formed is dissolvable in common solvents, the composition can be applied to a substrate as easily as a resist composition solution without requiring a special apparatus.
However, since the organic antireflection film made from a polyamide acid (co)polymer or polysulfone (co)polymer and a dye limits the amount of the dye that can be added, the film cannot sufficiently prevent halation and standing waves. In addition, because such an organic film migrates with a resist film in a slight amount (a phenomenon known as intermixing), a resist pattern may have an impaired sectional configuration (an impaired pattern profile) such as inadequate dyeing and a skirt shape.
On the other hand, a polymer having an acenaphthylene skeleton is known to overcome the above-described problems to a considerable extent, if applied to an antireflection film (see Japanese Patent Applications Laid-open No. 2000-143937 and No. 2001-402933, for example). The antireflection film, however, cannot necessarily overcome the problem of intermixing.
As a means for overcoming this problem, a method of crosslinking the polymer having an acenaphthylene skeleton with formaldehyde or the like is thought to be effective. This method, however, may impair storage stability of the antireflection film-forming composition stored in the form of a solution.
Development of an improved antireflection film that can overcome the problems in conventional technologies and development of a polymer useful as a polymer component for such an antireflection film have therefore been desired.
The subject of the present invention is to overcome the above-described problems in conventional technologies and provide an antireflection film-forming composition exhibiting high antireflection effect and capable of forming resist patterns excelling in resolution, pattern configuration, and the like, without intermixing, to provide a polymer useful particularly as a component for the antireflection film-forming composition, and to provide acenaphthylene derivatives useful particularly as a raw material or an intermediate for the polymer.
As a result of extensive studies to solve the above problems, the inventors of the present invention have found that a novel acenaphthylene derivative easily synthesized from a readily available acenaphthene by a process involving well-known organic synthesis reactions is very useful as a raw material or an intermediate for a polymer that can effectively solve the above problems relating to antireflection films. The inventors have further found that a novel polymer having an aromatic ring with a specific substituent that can be produced from the acenaphthylene derivative exhibits a high absorbance of an excimer laser or other radiations and a high refractive index in comparison with conventional antireflection films, and that excellent antireflection films can be produced by using the polymer as an antireflection film-forming composition. The findings have led to the completion of the present invention.